The present invention relates generally to radar receivers and more particularly to radar receivers which process target angle information in terms of amplitude or phase information.
Heretofore, radar receivers have been designed to either amplitude or phase encode the angle of the target with respect to the antenna boresight. In an amplitude sensitive system, sum and difference signals derived from a monopulse comparator are added in phase in the receiver to produce .SIGMA.+.DELTA. and .SIGMA.-.DELTA. signals. A major advantage of this approach is that the target angle is proportional to .DELTA./.SIGMA. which is easy to compute in a radar signal processor. A second advantage is that the two receiver channels (.SIGMA. and .DELTA.) do not require close phase matching. A major disadvantage of the amplitude encoding system is its vulnerability to gain saturation. For signals large enough to saturate the receiver, the .SIGMA. and .DELTA. magnitude data is not valid and the angle information is lost.
The second type of radar receiver operates in a manner which phase encodes the target angle information. In this radar system, the receiver combines the .SIGMA. and .DELTA. signals in quadrature to produce the .SIGMA.+j.DELTA. and .SIGMA.-j.DELTA. signals. The target angle is proportional to .phi.(.SIGMA.+j.DELTA.)-.phi.(.SIGMA.-j.DELTA.). This system tracks the target angle in the presence of large signals, but requires a complex signal processor to do so. In addition, phase matching between the two receiver channels is required.
Because of the differing advantages and disadvantages of the two detection schemes, it would be an improvement in the radar art to have a radar receiver which is capable of detecting target information in terms of both amplitude and phase information.